3MF to STEP
Convert 3MF to STEP: every object on the build plate as a faceted solid for CAD, in millimetres.
How it works
Open the 3MF
Drop the mesh: STL, OBJ, 3MF, PLY, GLB or glTF. It is read in your browser, shown in 3D and checked for holes; tick Repair if it has any, so it can become a solid.
Flat areas become faces
Every flat region of the mesh is joined into one planar face with straight edges, holes and all, so a box comes out as six faces, not twelve triangles. A closed mesh is written as one solid.
Download the STEP
Open it in Fusion 360, SolidWorks, Onshape, FreeCAD or any CAD program to measure it, cut it, add holes and fillets, or use it in an assembly.
3MF to STEP converter: free and online
Convert 3MF to STEP in your browser: drop in a 3MF file and download the STEP. The file is converted on your own device and never uploaded, so this 3mf to step converter is safe for private and confidential files.
3MF is the modern 3D printing format, holding units and colour where STL cannot.
The paths come out at the real size you set, in millimetres or inches, ready for a laser, a CNC router, a vinyl cutter or a plotter.
More conversions from 3MF: 3MF to STL, 3MF to OBJ.
Other conversions to STEP: STL to STEP, OBJ to STEP.
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Why it matters
The right way up and the right size
A 20 mm part stays 20 mm and upright: glTF's metres and Y-up axis are converted to and from the millimetres and Z-up of STL, 3MF and slicers.
Checked against a reference
Every format pair is tested against trimesh: the same volume, surface area and size come back out.
Nothing uploaded
Client parts and unreleased designs stay on your computer. The model is read and written in this tab.
Questions
How do I convert 3MF to STEP?
Drop your 3MF file on this page, check the preview, and press Download. The STEP is made in a few seconds, with no sign-up.
Is my 3MF file uploaded anywhere?
No. The 3mf to step conversion runs in your browser, on your own device. The file never leaves it.
Is the 3MF to STEP file a real solid?
Yes, when the mesh is closed: it is written as a MANIFOLD_SOLID_BREP in an AP214 STEP file, which CAD programs open as a solid body you can cut, extrude into and measure. A mesh with holes is written as a surface instead, and the page says so; tick Repair to close it first.
Will curved surfaces be smooth?
No. A mesh no longer knows it was a cylinder or a fillet, so curves stay as the flat facets the mesh had: a 48-sided cylinder becomes 48 flat side faces and two caps. Flat areas are joined into single faces. Fitting true curves back (reverse engineering) is a different job.
Is it checked?
Each STEP is read back by OpenCASCADE, the kernel FreeCAD is built on: a box comes back as 6 faces, a plate with a square hole as 10 faces with the hole as an inner boundary, a 48-sided cylinder as 50 faces, each with the same volume as the mesh.
How big a mesh can it take?
Up to 100,000 triangles. Every face is about 1 KB of STEP, and CAD programs are slow with many faces: OpenCASCADE took 42 seconds to open a 20,480-face sphere. For a dense scan, reduce it first (Blender Decimate or the slicer).
Which 3D formats can I convert?
STL (binary and ASCII), OBJ, PLY (ASCII and binary), OFF, 3MF, GLB and glTF, in and out, in any combination.
Are colours and textures kept?
No: the shape is converted, every triangle of it, but not colours, textures or materials. The page says when the file had them. For printing and CAD that is what matters; for a textured game asset, keep the GLB.
Why is my glTF so small or lying on its side?
glTF measures in metres and stands models on the Y axis; STL and slicers use millimetres and the Z axis. This converter turns and scales between them, and "Keep axes and units as they are" turns that off.
Can it convert STEP or IGES?
Yes, into any of the mesh formats: drop the .step, .stp, .iges or .igs file and OpenCASCADE cuts its solids into triangles in your browser. The other way, a mesh is saved as a STEP solid made of flat faces (see the STL to STEP converter).
What about compressed glTF?
Draco and meshopt compressed glTF files are recognised and reported; export them again without mesh compression to convert them here.